Working with JSON and YAML

import json
import yaml
from pathlib import Path

# ===== JSON PARSING =====
# JSON string to Python dict
json_str = '{"hostname": "web01", "port": 8080, "ssl": true}'
data = json.loads(json_str)
print(data["hostname"])     # "web01"
print(data["port"])         # 8080 (int, not string!)

# JSON null becomes Python None
json_with_null = '{"status": null}'
parsed = json.loads(json_with_null)
print(parsed["status"])     # None

# ===== JSON FROM FILE =====
with open("config.json", "r") as f:
    config = json.load(f)   # note: load() not loads()
    print(config)

# ===== PYTHON TO JSON =====
# Python dict to JSON string
deployment = {
    "apiVersion": "apps/v1",
    "kind": "Deployment",
    "metadata": {"name": "web-app"},
    "spec": {"replicas": 3}
}
json_output = json.dumps(deployment, indent=2)  # indent for readability
print(json_output)

# ===== JSON TO FILE =====
with open("deployment.json", "w") as f:
    json.dump(deployment, f, indent=2)

# ===== YAML PARSING =====
yaml_str = """
hostname: web01
port: 8080
ssl: true
tags:
  - production
  - monitored
services:
  - name: nginx
    status: running
  - name: postgres
    status: stopped
"""

data = yaml.safe_load(yaml_str)
print(data["hostname"])         # "web01"
print(data["port"])             # 8080
print(data["tags"])             # ['production', 'monitored']
print(data["services"][0])      # {"name": "nginx", "status": "running"}

# ===== YAML FROM FILE =====
with open("deployment.yaml", "r") as f:
    manifest = yaml.safe_load(f)
    replicas = manifest["spec"]["replicas"]
    print(f"Replicas: {replicas}")

# ===== YAML MULTILINE STRINGS =====
# YAML supports multiline text
yaml_multiline = """
script: |
  #!/bin/bash
  echo "Deploying..."
  kubectl apply -f deployment.yaml
description: >
  This script deploys the application
  to the Kubernetes cluster
"""

parsed = yaml.safe_load(yaml_multiline)
print(parsed["script"])
# #!/bin/bash
# echo "Deploying..."
# kubectl apply -f deployment.yaml

# ===== PYTHON TO YAML =====
config = {
    "apiVersion": "v1",
    "kind": "ConfigMap",
    "metadata": {"name": "app-config"},
    "data": {
        "log_level": "INFO",
        "debug": False
    }
}

yaml_output = yaml.dump(config, default_flow_style=False)
print(yaml_output)

# Write to file
with open("configmap.yaml", "w") as f:
    yaml.dump(config, f, default_flow_style=False)

# ===== WORKING WITH NESTED DATA =====
# Access nested values safely
deployment = {
    "metadata": {"name": "app"},
    "spec": {"replicas": 3, "selector": {"matchLabels": {"app": "web"}}}
}

# Direct access (risky if key missing)
name = deployment["metadata"]["name"]

# Safe access using .get()
replicas = deployment.get("spec", {}).get("replicas")   # returns None if missing

# ===== TRANSFORMING DATA =====
# Kubernetes Deployment to scaled-down version
full_deployment = {
    "apiVersion": "apps/v1",
    "kind": "Deployment",
    "metadata": {"name": "web-app", "namespace": "default"},
    "spec": {
        "replicas": 3,
        "selector": {"matchLabels": {"app": "web"}},
        "template": {
            "metadata": {"labels": {"app": "web"}},
            "spec": {"containers": [{"name": "web", "image": "nginx:latest", "ports": [{"containerPort": 80}]}]}
        }
    }
}

# Extract just the essential parts for a smaller manifest
minimal = {
    "apiVersion": full_deployment["apiVersion"],
    "kind": full_deployment["kind"],
    "metadata": {"name": full_deployment["metadata"]["name"]},
    "spec": {"replicas": 1}  # Reduce replicas
}

# ===== VALIDATION =====
# Check if required fields exist
def validate_deployment(deploy_dict):
    """Check if deployment has required fields."""
    required_fields = ["apiVersion", "kind", "metadata", "spec"]
    for field in required_fields:
        if field not in deploy_dict:
            raise ValueError(f"Missing required field: {field}")
    if deploy_dict["kind"] != "Deployment":
        raise ValueError("kind must be 'Deployment'")
    return True

# ===== READING MULTIPLE FILES =====
yaml_dir = Path("./manifests")
all_manifests = []

for yaml_file in yaml_dir.glob("*.yaml"):
    with open(yaml_file) as f:
        manifest = yaml.safe_load(f)
        all_manifests.append(manifest)

print(f"Loaded {len(all_manifests)} manifests")

# ===== COMMON PITFALL: JSON IN JSON =====
# API returns a JSON string containing JSON
api_response = '{"data": "{\\"name\\": \\"app\\"}"}'
outer = json.loads(api_response)
inner = json.loads(outer["data"])
print(inner["name"])  # "app"

# ===== USE SAFE_LOAD FOR YAML =====
# Never use yaml.load() — always use yaml.safe_load()
# load() can execute arbitrary Python code (security risk)
# safe_load() only constructs simple Python objects
data = yaml.safe_load(yaml_str_untrusted)  # SAFE
# data = yaml.load(yaml_str_untrusted)      # DANGEROUS